Fourth-generation Fluoroquinolone Antibiotics Research Articles

Evaluation of growth and antioxidant responses of freshwater microalgae Chlorella sorokiniana and Scenedesmus dimorphus under exposure of moxifloxacin

As one of the fourth-generation fluoroquinolone antibiotics, moxifloxacin (MOX) has been frequently released to the aquatic environment, threatening local organisms. However, researches on its ecotoxicity to aquatic organisms are still limited. This study analyzed effects of MOX on the growth, photosynthesis and oxidative stress of two common types of freshwater microalgae, Chlorella sorokiniana and Scenedesmus dimorphus. The 96 h-EC50 values of MOX for C. sorokiniana and S. dimorphus were 28.42 and 26.37 mg/L, respectively. Although variations of specific indicators for photosynthetic fluorescence intensity were different, photosystems of two types of microalgae were irreversibly damaged. The malondialdehyde content and superoxide dismutase of C. sorokiniana and S. dimorphus evidently increased, indicating that the exposure of MOX caused serious oxidative stress. Chlorophyll a, b and carotenoids contents of C. sorokiniana increased, probably resulting from the resistance to oxidative stress, whereas they were inhibited due to oxidation damage as for S. dimorphus. Risk quotients (RQs) of MOX for C. sorokiniana and S. dimorphus in wastewater were 7.882 and 8.495, respectively, which demonstrated that MOX had a considerable risk to aquatic environment, especially in the context of its increasing use in practice.

Besifloxacin Nanocrystal: Towards an Innovative Ophthalmic Preparation.

Bacterial conjunctivitis significantly impacts public health, including more than one-third of eye diseases reported worldwide. It is an infection caused by various aerobic and anaerobic bacteria and is highly contagious. Therefore, it has a high incidence of bacterial resistance to the antibiotics commonly used for treatment. Among the most recent antibiotics, besifloxacin is a fourth-generation fluoroquinolone antibiotic indicated exclusively for topical ophthalmic use. Due to its importance in treating bacterial conjunctivitis and its low solubility in water, limiting its efficacy, a nanotechnology-based drug delivery preparation was developed to overcome this hurdle. Besifloxacin nanocrystals were prepared by small-scale wet milling and response surface methodology, using Povacoat® as a stabilizer. The particle’s average hydrodynamic diameter (Z-ave) was approximately 550 nm (17 times smaller than raw material), with a polydispersity index (PdI) of less than 0.2. The saturation solubility increased about two times compared to the raw material, making it possible to increase the dissolution rate of this drug substance, potentially improving its bioavailability and safety. The optimized preparation was stable under an accelerated stability study (90 days). The Z-ave, PZ, PdI, and content did not alter significantly during this period. Furthermore, the 0.6% m/m besifloxacin nanocrystals at the maximum dose and the Povacoat® stabilizer did not show toxicity in Galleria mellonella larvae. The innovative ophthalmic preparation minimum inhibitory concentration (MIC) was 0.0960 µg/mL and 1.60 µg/mL against Staphylococcus aureus and Pseudomonas aeruginosa, respectively, confirming in vitro efficacy. Therefore, besifloxacin nanocrystals revealed the potential for reduced dosing of the drug substance, with a minor occurrence of adverse effects and greater patient adherence to treatment.

Effects of moxifloxacin and gatifloxacin stress on growth, photosynthesis, antioxidant responses, and microcystin release in Microcystis aeruginosa

Moxifloxacin (MOX) and gatifloxacin (GAT) are fourth-generation fluoroquinolone antibiotics that are frequently detected in surface water environments and pose a threat to aquatic organisms. However, research into their toxicity to Microcystis aeruginosa, a cyanobacterium, has thus far been limited. In the present study, we investigated the effects of these antibiotics on M. aeruginosa growth, photosynthesis, oxidative stress, and microcystin (MC) release. The results of the 96 h EC50 values of MOX and GAT were 60.34 and 25.30 μg/L, respectively, and the risk quotients calculated indicated that these antibiotics could pose considerable ecological risks at actual environmental concentrations. Photosynthetic fluorescence intensity was shown to decline markedly, and Fv/Fm significantly decreased without any evidence of recovery, suggesting that the organism’s photosystems were irreversibly damaged. Chlorophyll a and carotenoid content decreased, whereas the ratio of carotenoids to chlorophyll a increased, indicating that carotenoids were less susceptible to damage than chlorophyll a. The reactive oxygen species and malondialdehyde content significantly increased, as well as the superoxide dismutase and catalase activities, indicating that exposure caused serious oxidative stress. Additionally, MC release increased. These results demonstrate that the environmental risks posed by MOX and GAT should be given serious consideration, particularly as their use is increasing.

Development and optimization of besifloxacin hydrochloride loaded liposomal gel prepared by thin film hydration method using 32 full factorial design

The objective of this present research work was to develop and optimize a liposomal gel containing a fourth generation fluoroquinolone antibiotic, besifloxacin hydrochloride (BSF−HCl), for ocular delivery using factorial design. The ocular delivery of BSF−HCl loaded liposomal gels may produce improve the ocular bioavailability with increased residence time of drug in the cornea and decreasing the non-productive absorption of besifloxacin hydrochloride. Besifloxacin hydrochloride loaded liposomes were prepared by thin-film hydration technique. The effect of two independent factors (soya lecithin to cholesterol ratio and lipid to drug ratio) on characteristics of liposomes i.e. responses (entrapment efficiency, drug loading and particle size) were examined. A quadratic polynomial model equation was generated to predict the relationship between independent factors and the responses. The in vitro drug release from the optimized liposomes exhibited biphasic release pattern for the initial rapid release and subsequently sustained drug release. The optimized liposomes (F1) were incorporated into a gel containing carbopol 940, tri-ethanolamine and glycerol. The optimized BSF−HCl loaded liposome formulation (F1) showed the encapsulation efficiency, drug loading and particle size of 41.01 ± 1.22%, 10.84 ± 0.46% and 436.8 ± 23.4 nm, respectively. The ex-vivo corneal permeation of the drug loaded liposomal gel demonstrated a significant (p < 0.05) increment of BSF−HCl permeation than the BSF−HCl loaded gel and the histological study on the pig cornea showed no corneal drainage even after 8 h of application. Thus, the developed BSF−HCl loaded liposomal gel could be used as an effective ocular drug delivery system to treat bacterial infections.

Study of degradation behavior of besifloxacin, characterization of its degradation products by LC-ESI-QTOF-MS and their in silico toxicity prediction.

Knowledge and understanding of the stability profile of a drug is important as it affects its safety and efficacy. In the present work, besifloxacin, a new, fourth-generation fluoroquinolone antibiotic, was subjected to different forced-degradation conditions as per International Conference on Harmonization (ICH) guidelines such as hydrolysis (acid, base and neutral), oxidation, thermal and photolysis. The drug degraded under acidic, basic, oxidative and photolytic conditions while it was found to be stable under dry heat and neutral hydrolytic conditions. In total, five degradation products (DPs) were formed under different conditions-DP1 and DP2 (photolysis), DP3 (oxidation), DP4 (acidic), DP3 and DP5 (basic). The chromatographic separation of besifloxacin and its degradation products was achieved on a Sunfire C18 (250 mm × 4.6 mm, 5 μm) column with 0.1% aqueous formic acid-acetonitrile as a mobile phase. The gradient RP-HPLC method was developed and validated as per ICH guidelines. The degradation products were characterized with the help of LC-ESI-QTOF mass spectrometric studies and the most likely degradation pathway of the drug was proposed. In silico toxicity assessment of the drug and its degradation products was carried out, which indicated that DP3 and DP4 carry a mutagenicity alert.

Alterations of Genes Involved in Apoptosis and Epigenetic Modulation Associated with Gatifloxacin-Induced Oxidative Stress in Rat Liver

Introduction Gatifloxacin (1-Cyclopropyl-1,4-dihydro-6-fluoro-8-methoxy-7-(3-methyl-1-piperazinyl)-4-oxo-3-quinolinecarboxylic acid, DB01044) is a member of the fourth-generation fluoroquinolone antibiotic family that is used in treating infection caused by a broad range of microorganisms. It fun

Design and characterization of multifaceted lyophilized liposomal wafers with promising wound healing potential

Various dressings are available to heal chronic wounds which many times fail to achieve the expected results. To overcome some of their drawbacks, formulation of a novel dressing; lyophilized liposomal wafers having better wound healing potential has been proposed in the present study. The drug incorporated in the formulation is gatifloxacin (GTX) which is a fourth-generation fluoroquinolone antibiotic having in vitro activity against both Gram-negative and Gram-positive bacteria. The formulation was designed in three stages where at first liposomes were prepared, the liposomes were converted to gel using chitosan and lastly this gel was lyophilized to form liposomal wafers. Liposomes were prepared by varying the concentration of lipid and cholesterol and evaluated for particle size, entrapment efficiency, in vitro cumulative release, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Liposomes were converted to liposomal gel using chitosan and evaluated for texture, clarity, viscosity, spreadibility and in vitro drug release. Finally, this liposomal batch was subjected to lyophilization to convert it to liposomal wafers and subjected to SEM, differential scanning calorimetric, X-ray diffraction and drug release studies. The in vivo studies were carried out on Wistar rats where wound healing potential of the wafers was confirmed by histopathological evaluation.

In vivo 3D measurement of moxifloxacin and gatifloxacin distributions in the mouse cornea using multiphoton microscopy.

Moxifloxacin and gatifloxacin are fourth-generation fluoroquinolone antibiotics used in the clinic to prevent or treat ocular infections. Their pharmacokinetics in the cornea is usually measured from extracted ocular fluids or tissues, and in vivo direct measurement is difficult. In this study multiphoton microscopy (MPM), which is a 3D optical microscopic technique based on multiphoton fluorescence, was applied to the measurement of moxifloxacin and gatifloxacin distribution in the cornea. Intrinsic multiphoton fluorescence properties of moxifloxacin and gatifloxacin were characterized, and their distributions in mouse cornea in vivo were measured by 3D MPM imaging. Both moxifloxacin and gatifloxacin had similar multiphoton spectra, while moxifloxacin had stronger fluorescence than gatifloxacin. MPM imaging of mouse cornea in vivo showed (1) moxifloxacin had good penetration through the superficial corneal epithelium, while gatifloxacin had relatively poor penetration, (2) both ophthalmic solutions had high intracellular distribution. In vivo MPM results were consistent with previous studies. This study demonstrates the feasibility of MPM as a method for in vivo direct measurement of moxifloxacin and gatifloxacin in the cornea.

Modeling, Optimization, and In Vitro Corneal Permeation of Chitosan-Lomefloxacin HCl Nanosuspension Intended for Ophthalmic Delivery

Lomefloxacin HCl (LF) is a widely used fourth-generation fluoroquinolone antibiotic. Like most drug solutions administered via ocular route, it is usually eliminated by eye protective mechanisms. Chitosan (CS) is a natural polysaccharide polymer with numerous advantages in ocular delivery with, antibacterial, and antifungal properties. The aims were to formulate and optimize LF nanosuspensions (NS) with enhanced antimicrobial activity and prolonged duration using ionic gelation technique. Formulation variables included drug load, CS concentration, crosslinker type (tripolyphosphate and sodium alginate), and concentration. Nanosuspension properties (particle size, zeta potential, polydispersity index, entrapment efficiency, drug release, and permeation through bovine cornea) were evaluated. The artificial neural networks (ANNs) model showed optimum entrapment efficiency of 70.63 % w/w, particle size of 176 ± 0.28 nm, and zeta potential of 13.65 mV. Transmission electron microscopy illustrated the production of well-defined spherical nanoparticles. The nanosuspensions showed prolonged release of LF for more than 8 h and threefold increase in amount permeated through bovine cornea compared to drug solution. Improved antibacterial activity of the nanosuspension was noted where 2- and 3.5-fold decrease in minimum inhibitory concentration (MIC) of drug against Gram-positive and Gram-negative bacteria were observed, respectively. Twofold decrease in minimum bactericidal concentration (MBC) of drug nanosuspension against both types of bacteria was also demonstrated. Histopathological examination showed compatibility of optimized formulation with eye tissues in rabbit model. Therefore, model-optimized LF nanosuspension could be an ideal solution to ocular infections by virtue of their augmented activity, high compatibility, and improved permeability.

Characteristics of Endophthalmitis in Patients With the Boston Keratoprosthesis

To determine the characteristics of endophthalmitis in patients with the Boston keratoprosthesis. Retrospective chart review of 4 out of 35 patients who underwent implantation of the Boston keratoprosthesis on the Wills Eye Cornea service between 2001 and 2007 and developed infectious endophthalmitis. All 4 patients had keratoprosthesis surgery due to previous corneal transplant failure. The incidence of endophthalmitis was 11.4%. All patients were on topical antibiotic prophylaxis with a fluoroquinolone and 1 of the 4 patients was also using vancomycin drops. All 4 patients underwent a tap and inject and were admitted for intensive intravenous and topical antibiotics for 3 to 7 days. Culture positive results were found in 3 of the 4 vitreous samples: 2 coagulase-negative Staphylococcus, and 1 Pseudomonas and Staphylococcus aureus. Minimum Inhibitory Concentration data showed high resistance to fourth-generation fluoroquinolone antibiotics in all isolates. All patients recovered significant vision, except 1 patient who developed fluctuating vision secondary to vitreoretinal traction bands, which developed secondary to the endophthalmitis. Endophthalmitis can occur after Boston keratoprosthesis at a significant rate, even in low-risk patients on prophylactic antibiotic drops. Given our experience with these patients and vancomycin, we recommend its prophylactic use. The increasing resistance of gram-positive organisms to fluoroquinolones and the need for close patient follow-up to encourage adherence to preventive regimens are further supported in this report.

Poster 10: Breakthrough Keratitis Following PRK

To determine whether the penetration into the aqueous humor of 2 new fourth-generation fluoroquinolone antibiotics, gatifloxacin (Zymar) and moxifloxacin (Vigamox) eyedrops, was affected by different methods of administration before cataract surgery.Pasqua Hospital, Regina, Saskatchewan, Canada.This prospective randomized study comprised 193 patients. The patients were divided into 2 main groups. One group received gatifloxacin eyedrops and the other, moxifloxacin eyedrops. Each group was subdivided into 4 subgroups. All patients received the drops 4 times a day starting 2 days preoperatively. The first subgroup did not receive any more antibiotics. The second subgroup received the antibiotic drops 3 times, starting approximately 2 hours preoperatively. The third subgroup received a wick soaked in a dilating mixture containing the antibiotic. The fourth subgroup received the wick and the antibiotic drops at the time of preparation for surgery. At the beginning of surgery, 0.1 mL of aqueous humor was aspirated, frozen, and sent under ice by courier to the Provincial Laboratory for analysis by high-performance liquid chromatography.The study included 124 women and 69 men. The mean concentrations in the aqueous humor were 0.19, 0.82, 0.22, and 0.30 μg/mL in the 4 gatifloxacin subgroups, respectively, and 0.38, 2.16, 0.88, and 0.97 μg/mL in the 4 moxifloxacin subgroups, respectively. Analysis of variance showed the differences between the 2 antibiotics to be statistically significant.Moxifloxacin penetrated the aqueous humor better than gatifloxacin regardless of the method of administration. Both antibiotics penetrated the aqueous humor well when given in drop form. They reached and exceeded the minimum inhibitory concentration levels for the most common ocular pathogens causing endophthalmitis. Only moxifloxacin reached these levels when the wick was used.

Aqueous humor penetration of gatifloxacin and moxifloxacin eyedrops given by different methods before cataract surgery

To determine whether the penetration into the aqueous humor of 2 new fourth-generation fluoroquinolone antibiotics, gatifloxacin (Zymar) and moxifloxacin (Vigamox) eyedrops, was affected by different methods of administration before cataract surgery. Pasqua Hospital, Regina, Saskatchewan, Canada. This prospective randomized study comprised 193 patients. The patients were divided into 2 main groups. One group received gatifloxacin eyedrops and the other, moxifloxacin eyedrops. Each group was subdivided into 4 subgroups. All patients received the drops 4 times a day starting 2 days preoperatively. The first subgroup did not receive any more antibiotics. The second subgroup received the antibiotic drops 3 times, starting approximately 2 hours preoperatively. The third subgroup received a wick soaked in a dilating mixture containing the antibiotic. The fourth subgroup received the wick and the antibiotic drops at the time of preparation for surgery. At the beginning of surgery, 0.1 mL of aqueous humor was aspirated, frozen, and sent under ice by courier to the Provincial Laboratory for analysis by high-performance liquid chromatography. The study included 124 women and 69 men. The mean concentrations in the aqueous humor were 0.19, 0.82, 0.22, and 0.30 microg/mL in the 4 gatifloxacin subgroups, respectively, and 0.38, 2.16, 0.88, and 0.97 microg/mL in the 4 moxifloxacin subgroups, respectively. Analysis of variance showed the differences between the 2 antibiotics to be statistically significant. Moxifloxacin penetrated the aqueous humor better than gatifloxacin regardless of the method of administration. Both antibiotics penetrated the aqueous humor well when given in drop form. They reached and exceeded the minimum inhibitory concentration levels for the most common ocular pathogens causing endophthalmitis. Only moxifloxacin reached these levels when the wick was used.

Acute Endophthalmitis in Eyes Treated Prophylactically with Gatifloxacin and Moxifloxacin

To study the use of prophylactic fourth-generation fluoroquinolone antibiotics, gatifloxacin and moxifloxacin, and bacterial sensitivity in cases of acute postoperative endophthalmitis following cataract surgery. Retrospective, consecutive, observational case series. Forty-two eyes of 42 patients with acute endophthalmitis occurring within six weeks after cataract surgery were identified. All patients were seen in a referral vitreoretinal practice over a two-year time interval. The number of patients using prophylactic gatifloxacin or moxifloxacin and results of bacterial culture and sensitivity to all fluoroquinolone antibiotics were recorded. Thirty-one of 42 eyes (74%) were treated with perioperative gatifloxacin or moxifloxacin and 24 eyes (57%) were continuously taking one of these antibiotics at the time of diagnosis. Nineteen eyes (45%) had a positive bacterial culture. The most frequent organism isolated was coagulase-negative Staphylococcus. Sensitivities were performed for 14 gram-positive organisms, and sensitivities to ciprofloxacin (50%), ofloxacin (44%), levofloxacin (46%), gatifloxacin (38%), and moxifloxacin (38%) were noted. Five organisms were resistant to gatifloxacin and moxifloxacin with a minimum inhibitory concentration of 8 microg/ml. All gram-positive organisms were sensitive to vancomycin. Median visual acuity improved from hand motions to 20/40 at last follow-up. Acute endophthalmitis can develop after cataract surgery despite the prophylactic use of fourth-generation fluoroquinolone antibiotics. Gram-positive organisms causing acute endophthalmitis are frequently resistant to all fluoroquinolones, including a significant number of cases resistant to gatifloxacin and moxifloxacin.

Confocal Assessment of the Effects of Fourth-Generation Fluoroquinolones on the Cornea

To evaluate the toxicity of fourth-generation fluoroquinolone antibiotic solutions on the rabbit corneal epithelium. In vivo confocal microscopy was used to assess epithelial structure in 18 rabbits, and tight junction integrity of superficial epithelial cells was evaluated with ZO-1 labeling in 10 rabbits. Eyes were bathed with commercial solutions of moxifloxacin (Vigamox) or gatifloxacin (Zymar) solution for 3 minutes, rinsed with balanced salt solution, and immediately examined. Balanced salt solution rinsing alone served as the control. A decrease in epithelial cell size was observed after treatment with Zymar (P < 0.05, two-way repeated-measures analysis of variance), but not with Vigamox or the control. Normal ZO-1 organization was observed in controls and eyes treated with Vigamox. ZO-1 staining in eyes treated with Zymar was disrupted, patchy, and generally weaker than that in control eyes. After short-term, intensive exposure to Vigamox, corneal epithelial integrity and tight junction organization are maintained. Zymar induces a loss of superficial epithelial cells and breakdown of tight junctions under similar conditions.

Ophthalmic Infections and Their Anti-infective Challenges

This introduction provides an overview of the succeeding articles contained within this supplement on the new fourth-generation fluoroquinolone antibiotic product, moxifloxacin ophthalmic solution 0.5% (VIGAMOX®, Alcon Laboratories, Inc., Fort Worth, TX). Moxifloxacin was developed specifically to address the increasing incidence of resistance to earlier-generation antibiotic molecules. Structural modifications to the moxifloxacin molecule have decreased the likelihood of the development of resistant organisms. This antibiotic has been shown to possess greater activity than previous-generation molecules against gram-positive bacteria while maintaining excellent potency against gram-negative organisms and nontuberculous (atypical) mycobacteria. Moxifloxacin ophthalmic solution 0.5% exhibits enhanced bioavailability due to a unique molecular structure that combines high lipophilicity for enhanced corneal penetration with high aqueous solubility at physiological pH. Numerous studies have shown that moxifloxacin ophthalmic solution 0.5% has high potency against a broad range of microbial species and a favorable profile in terms of safety and tolerability. The results presented in this supplement provide additional evidence for the potential benefits of moxifloxacin ophthalmic solution 0.5% in surgical prophylaxis and treatment of sight-threatening infections, such as bacterial conjunctivitis, endophthalmitis and keratitis.

Vitreous and aqueous penetration of orally administered gatifloxacin in humans.

To investigate the penetration of gatifloxacin, a novel extended-spectrum fourth-generation fluoroquinolone antibiotic, into the vitreous and aqueous humor after oral administration. A prospective, nonrandomized study of 24 consecutive patients scheduled for pars plana vitrectomy between September 2001 and May 2002 at the Cullen Eye Institute. Aqueous, vitreous, and serum samples were obtained and analyzed from 24 patients after administration of two 400-mg gatifloxacin tablets taken 12 hours apart before the operation. Assays were performed using high-performance liquid chromatography. Mean +/- SD gatifloxacin concentrations in serum (n = 23), vitreous (n = 23), and aqueous (n = 11) were 5.14 +/- 1.36 micro g/mL, 1.34 +/- 0.34 micro g/mL, and 1.08 +/- 0.54 micro g/mL respectively. Mean +/- SD sampling times after oral administration of the second gatifloxacin tablet for serum, vitreous, and aqueous were 3.2 +/- 1.0 hours, 4.0 +/- 1.0 hours, and 3.9 +/- 1.1 hours, respectively. The percentages of serum gatifloxacin concentration achieved in the vitreous and aqueous were 26.17% and 21.02%, respectively. Mean inhibitory vitreous and aqueous MIC(90 ) levels were achieved against many pathogens, including Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Propionibacterium acnes, Haemophilus influenzae, Escherichia coli, Bacillus cereus, Proteus mirabilis, and other organisms. Orally administered gatifloxacin achieves therapeutic levels in the noninflamed human eye, and the activity spectrum appropriately encompass the bacterial species most frequently involved in the various causes of endophthalmitis. Because of its broad-spectrum coverage, low MIC(90) levels for the organisms of concern, and good tolerability, gatifloxacin represents a major advance in the prophylaxis or treatment of postoperative, posttraumatic, and bleb-associated bacterial endophthalmitis.